Dissolution test vessel with integral verticality control

Abstract

A vessel includes a cylindrical section coaxially disposed about a central axis of the vessel. The cylindrical section includes an inside vessel surface, an outside vessel surface opposing the inside vessel surface, an upper end region circumscribing a vessel opening, and a lower end region axially spaced from the upper end region. A bottom section is disposed at the lower end region. A flange is coaxially disposed about the central axis and extends radially outward from the outside vessel surface at the upper end region. The flange includes a bottom surface facing generally toward the lower end region and perpendicular to the inside vessel surface. A ring may be coaxially disposed about the central axis and provide the bottom surface. An annular shoulder may protrude from the outside vessel surface, and may be spaced from or integrally adjoined to the flange.

What is claimed is: 
     
       1. A vessel comprising:
 a cylindrical section coaxially disposed about a central axis of the vessel, the cylindrical section comprising an inside vessel surface, an outside vessel surface opposing the inside vessel surface, an upper end region circumscribing a vessel opening, and a lower end region axially spaced from the upper end region; 
 a bottom section disposed at the lower end region; 
 a flange coaxially disposed about the central axis, the flange comprising a main flange portion extending radially outward from the outside vessel surface at the upper end region, and a bottom surface facing generally toward the lower end region and perpendicular to the inside vessel surface, wherein the bottom surface lies in a horizontal plane and is entirely coplanar with the horizontal plane; and 
 a shoulder coaxially disposed about the central axis in the upper end region, the shoulder extending radially outward from the outside vessel surface and located axially between the flange and the lower end region, the shoulder comprising an outside shoulder surface concentric with the inside vessel surface relative to the central axis. 
 
     
     
       2. The vessel of  claim 1 , wherein the central axis is a vertical axis, and the bottom surface is entirely coplanar with the horizontal plane to within an accuracy of ±0.020°. 
     
     
       3. The vessel of  claim 1 , further comprising a ring coaxially disposed about the central axis and extending axially downward from the main flange portion, the ring terminating at a ring bottom surface wherein the ring bottom surface is axially distant from the main flange portion. 
     
     
       4. The vessel of  claim 3 , wherein the ring is radially spaced from the outside vessel surface by an annular groove formed in the flange. 
     
     
       5. The vessel of  claim 1 , wherein the shoulder is spaced from the flange. 
     
     
       6. The vessel of  claim 1 , wherein the inside vessel surface defines an inside vessel diameter of the cylindrical section, the outside shoulder surface defines an outside shoulder diameter of the shoulder, and the diametric difference between the inside vessel diameter and the outside shoulder diameter is uniform at any circumferential point relative to the central axis. 
     
     
       7. The vessel of  claim 1 , wherein the inside vessel surface defines an inside vessel diameter of the cylindrical section, the outside shoulder surface defines an outside shoulder diameter of the shoulder, and the diametric difference between the inside vessel diameter and the outside shoulder diameter varies by no greater than +/−0.05 inch at any circumferential point relative to the central axis. 
     
     
       8. The vessel of  claim 1 , wherein the shoulder integrally adjoins the flange. 
     
     
       9. A dissolution test apparatus comprising:
 a vessel support member comprising a top surface and an inside edge circumscribing an aperture; and 
 a vessel extending through the aperture and comprising:
 a cylindrical section coaxially disposed about a central axis of the vessel, the cylindrical section comprising an inside vessel surface, an outside vessel surface opposing the inside vessel surface, an upper end region circumscribing a vessel opening, and a lower end region axially spaced from the upper end region; 
 a bottom section disposed at the lower end region; 
 a flange coaxially disposed about the central axis, the flange comprising a main flange portion extending radially outward from the outside vessel surface at the upper end region, and a bottom surface facing generally toward the lower end region and perpendicular to the inside vessel surface, wherein the bottom surface lies in a horizontal plane and is entirely coplanar with the horizontal plane, wherein the inside vessel surface is parallel to the inside edge of the vessel support member; and 
 a shoulder coaxially disposed about the central axis in the upper end region, the shoulder extending radially outward from the outside vessel surface and located axially between the flange and the lower end region, the shoulder comprising an outside shoulder surface concentric with the inside vessel surface relative to the central axis, the outside shoulder surface abutting the inside edge of the aperture. 
 
 
     
     
       10. The dissolution test apparatus of  claim 9 , wherein the vessel further comprises a ring coaxially disposed about the central axis and extending axially downward from the main flange portion, the ring terminating at the bottom surface wherein the bottom surface is axially distant from the main flange portion. 
     
     
       11. The dissolution test apparatus of  claim 10 , wherein the ring is radially spaced from the outside vessel surface by an annular groove formed in the flange. 
     
     
       12. The dissolution test apparatus of  claim 9 , wherein the shoulder is spaced from the flange. 
     
     
       13. The dissolution test apparatus of  claim 12 , wherein the inside vessel surface defines an inside vessel diameter of the cylindrical section, the outside shoulder surface defines an outside shoulder diameter of the shoulder, and the diametric difference between the inside vessel diameter and the outside shoulder diameter is uniform at any circumferential point relative to the central axis. 
     
     
       14. The dissolution test apparatus of  claim 13 , further comprising an elongated structure extending into the vessel, wherein the outside shoulder surface and the inside vessel surface are concentric with the elongated structure. 
     
     
       15. The dissolution test apparatus of  claim 9 , wherein the shoulder integrally adjoins the flange. 
     
     
       16. The dissolution test apparatus of  claim 9 , further comprising an elongated structure extending into the vessel, wherein the inside vessel surface is parallel with the elongated structure. 
     
     
       17. A method for centering a vessel in an aperture of a vessel support member of a dissolution test apparatus, the aperture being coaxial with a vertical axis running through a center of the aperture, the method comprising:
 inserting the vessel through the aperture, the vessel comprising an inside vessel surface coaxially disposed about a central axis of the vessel, an outside vessel surface, a flange extending radially outward from the outside vessel surface, and a bottom surface extending axially downward from the flange and perpendicular to the inside vessel surface, wherein the vessel further comprises an annular shoulder protruding radially outward from the outside vessel surface, the annular shoulder comprising an outside shoulder surface concentric with the inside vessel surface relative to the central axis; and 
 supporting the vessel in a vertical orientation relative to the aperture by placing the bottom surface on a top surface of the vessel support member, wherein the entire inside vessel surface is parallel with the vertical axis. 
 
     
     
       18. The method of  claim 17 , further comprising inserting an elongated structure into the vessel, wherein the inside vessel surface is parallel with the elongated structure. 
     
     
       19. The method of  claim 17 , further comprising fixing the position of the vessel relative to the aperture at an elevation at which the outside shoulder surface abuts an inside edge of the vessel support member circumscribing the aperture, wherein the central axis of the vessel is aligned with the vertical axis at any polar position relative to the vertical axis. 
     
     
       20. The method of  claim 19 , further comprising inserting an elongated structure into the vessel, wherein the outside shoulder surface and the inside vessel surface are concentric with the elongated structure.